A good, well fit splint done by an expert dentist can help protect your teeth from your bruxing.

From what I've read, most soft splints don't do much. Even expensive splints made by a non-expert dentist can do more damage than good. I wore a flat plane occlusal splint for years. It was hard acrylic and custom made by my dentist. Turned out that while that splint protected my teeth it also contributed to my development of TMJD.

I had a repositioning splint that was around that price. It seems quite high for a sleep splint.

You don't say what kind of dentist you went to. If might be helpful to have a consultation with a Functional Orothdontist who is trained in sleep dentistry. They could probably create an appropriate splint for you with your full bite in mind.

My Functional Orthodontist created 2 splints for me. A functional orthodontist looks at the function of your bite in relation with your teeth and your body. One that was a daytime TMJD splint and another that was for night. Where my dentist had me wear a flat plane splint to protect my teeth, my orthodontist did a custom made splint that held my jaw in position and eventually kept me from bruxing at all. It was an upper splint, but not a flat plane splint and was only around $450. I cried when I got my braces and had to give up using it because it helped me so much.

In my opinion, before you spend that much money, I'd see a Functional Orothodontist/Sleep specialist. At least, that is what I'd do from the start if I knew then what I know now.